Towards maintaining canine training aid integrity: Effects of environmental factors and operational use on the triacetone triperoxide polymer odor capture-and-release system.

There are many factors that may affect the longevity of or guide the use of canine training aids. Literature to date has mainly focused on identifying the headspace volatiles associated with training aids or odors and only minimal research exists into how different variables may alter those volatiles. The current study examines several factors affecting canine training aids: humidity, air flow, transportation, and operational deployment, using the triacetone triperoxide polymer odor capture-and-release canine training aid (TATP POCR) as the target. The TATP POCR is an absorption-based canine training aid developed to be used to safely train canines to detect the odor of the explosive TATP in operational settings. Comparisons of the TATP POCR to neat TATP are made throughout the manuscript. First, humidity increased the background components of the POCR matrix, as well as the amount of TATP recovered was above the POCR. Humidity thus affected the amount of TATP detected but did not prevent detection. Second, air flow lessened the lifetime of the TATP POCR. Third, the practice of using primary and secondary containment successfully prevented contamination, cross-contamination, and significant target loss, thereby maintaining kit integrity. Finally, the absorption of background odors from training environments was not observed. TATP headspace concentrations between a Deployed and Control POCR kit were not significantly different at time 0 (i.e., upon opening), which suggests that the operational use does not affect the function of the TATP POCR system. This information provides pivotal evidence for explosives detection canine handlers or trainers who utilize the TATP POCR.

Do Saliva-Saturated Spit Hoods Interfere With Ventilation?

ABSTRACT: Spit hoods are used by law enforcement, officers in correctional facilities, and medical personnel during the restraint of agitated subjects that are actively spitting to prevent the transmission of droplet-transmitted pathogens. We could find no studies reporting on the time course of normal breathing to clear saliva from such a saturated spit hood. We purchased samples of 3 popular spit hood models and applied a section over the output of a pneumatic test system. We used a digital anemometer, digital manometer, and an inline controllable fan for back pressure and flow. The pressure was 3 mm Hg to match quiet breathing. The tested area was saturated with artificial saliva, and air pressure was applied while we recorded the pressure and airflow. Within 5 seconds, the spit hoods all cleared sufficient artificial saliva to allow 1 m/s of airflow, which exceeds that of an N95 mask with similar pressure. Commonly used spit hoods offer very low resistance to breathing even after being initially saturated with artificial saliva. Our results do not support the hypothesis that a saliva-filled spit hood might contribute to death.

Tropical Atlantic multidecadal variability is dominated by external forcing.

The tropical Atlantic climate is characterized by prominent and correlated multidecadal variability in Atlantic sea surface temperatures (SSTs), Sahel rainfall and hurricane activity1-4. Owing to uncertainties in both the models and the observations, the origin of the physical relationships among these systems has remained controversial3-7. Here we show that the cross-equatorial gradient in tropical Atlantic SSTs-largely driven by radiative perturbations associated with anthropogenic emissions and volcanic aerosols since 19503,7-is a key determinant of Atlantic hurricane formation and Sahel rainfall. The relationship is obscured in a large ensemble of CMIP6 Earth system models, because the models overestimate long-term trends for warming in the Northern Hemisphere relative to the Southern Hemisphere from around 1950 as well as associated changes in atmospheric circulation and rainfall. When the overestimated trends are removed, correlations between SSTs and Atlantic hurricane formation and Sahel rainfall emerge as a response to radiative forcing, especially since 1950 when anthropogenic aerosol forcing has been high. Our findings establish that the tropical Atlantic SST gradient is a stronger determinant of tropical impacts than SSTs across the entire North Atlantic, because the gradient is more physically connected to tropical impacts via local atmospheric circulations8. Our findings highlight that Atlantic hurricane activity and Sahel rainfall variations can be predicted from radiative forcing driven by anthropogenic emissions and volcanism, but firmer predictions are limited by the signal-to-noise paradox9-11 and uncertainty in future climate forcings.

Forced changes in the Pacific Walker circulation over the past millennium.

The Pacific Walker circulation (PWC) has an outsized influence on weather and climate worldwide. Yet the PWC response to external forcings is unclear1,2, with empirical data and model simulations often disagreeing on the magnitude and sign of these responses3. Most climate models predict that the PWC will ultimately weaken in response to global warming4. However, the PWC strengthened from 1992 to 2011, suggesting a significant role for anthropogenic and/or volcanic aerosol forcing5, or internal variability. Here we use a new annually resolved, multi-method, palaeoproxy-derived PWC reconstruction ensemble (1200-2000) to show that the 1992-2011 PWC strengthening is anomalous but not unprecedented in the context of the past 800 years. The 1992-2011 PWC strengthening was unlikely to have been a consequence of volcanic forcing and may therefore have resulted from anthropogenic aerosol forcing or natural variability. We find no significant industrial-era (1850-2000) PWC trend, contrasting the PWC weakening simulated by most climate models3. However, an industrial-era shift to lower-frequency variability suggests a subtle anthropogenic influence. The reconstruction also suggests that volcanic eruptions trigger El Niño-like PWC weakening, similar to the response simulated by climate models.

Using Fume Hood to Reduce Nurses' Exposure to Particulate Matters Dispersed Into the Air During Pill Crushing.

BACKGROUND: Pill crushing is a common practice in patient care settings. Crushing pills can disperse particulate matter (PM) into indoor air. The PM is a widespread air pollutant composed of microscopic particles and droplets of various sizes and may carry active and/or inactive ingredients nurses can inhale. This study aimed to quantify PM sizes and concentration in indoor air when pills are crushed and examine the role of a fume hood in reducing particulate pollution. METHODS: Two scenarios (with and without a fume hood) representing nurses' pill-crushing behaviors were set up in a positive-pressure cleanroom. Two acetaminophen tablets (325 mg/tablet) were crushed into powder and mixed with unsweetened applesauce. The PM sizes and concentrations were measured before and during crushing. RESULTS: Different sizes of PM, including inhalable, respirable, and thoracic particles, were emitted during medication crushing. The total count of all particle sizes and mass concentrations of particles were significantly lower during crushing when a fume hood was used (p = .00). CONCLUSION: Pill crushing increases PM and should be considered a workplace safety health hazard for nurses. Healthcare professionals should work under a fume hood when crushing pills and wear proper protective equipment. The findings of significant particulate pollution related to pill crushing suggest that further research is warranted.

Air circulation study inside and outside of urban buses induced by the opening of windows.

In this work, the external and internal airflow analysis in an urban bus is carried out through computational fluid dynamics. The research addresses the study of the internal flow to estimate the air change rate caused by the opening of windows. Two cases are considered: fully opening and partially opening the windows, and three bus speeds of 20, 40, and 60 km/h are assessed. The quantification of the air flow rate through the windows clearly displays that air enters through the rear windows and exits the bus through the front windows. This effect is explained by the pressure distribution in the outer of the bus, which causes the suction of the indoor air. At low bus speeds, the incoming air flow rate increases linearly with the speed, but the improvement is lower for high speeds. The theoretical air change time at 20 km/h is around 25.7 s, which is 9 times lower than expected by using HVAC systems. On the other hand, the estimation of the real air renewal time by solving a concentration shows that 40 s are needed to exchange 85% of the internal air of the bus. The research also assesses the effect of different levels of occupation inside the bus. Results are conclusive to recommend the circulation with full or partial window opening configurations in order to reduce the risk of airborne disease transmission.

Research on the relationship between the centerline velocity, aspect ratio and exhaust airflow rate for a slot and a rectangular capture hood in an local exhaust ventilation system.

When using a local exhaust hood to remove harmful substances from the production process, the exhaust airflow rate must be calculated according to the capturing velocity specified by the relevant regulations. The Numano and American Conference of Governmental Industrial Hygienists (ACGIH) equations are used in Japan and the US, respectively, for estimating the exhaust airflow rate of slot hoods. However, these equations differ from each other, and when using these equations to calculate the exhaust airflow rate of the capture hood, whether using Japan's equation or ACGIH, the hood type (slot or rectangular hood) should be distinguished at first. Therefore, this study performs experiments and a computational fluid dynamics (CFD) simulation to investigate the relationship between the centerline velocity and the aspect ratio for five types of capture hoods. The results showed good agreement between simulated and experimental centerline velocities when the distance from the hood face. A dimensionless velocity was introduced and a significant difference in the relationship between the centerline velocity and the distance from the hood face with different aspect ratios was found. A unified equation was obtained that can express the relationship between exhaust airflow rate and centerline velocity regardless of the aspect ratio of the hood face of the free-standing capture hood.

Current and potential approaches on assessing airflow and particle dispersion in healthcare facilities: a systematic review.

An indoor environment in a hospital building requires a high indoor air quality (IAQ) to overcome patients' risks of getting wound infections without interrupting the recovery process. However, several problems arose in obtaining a satisfactory IAQ, such as poor ventilation design strategies, insufficient air exchange, improper medical equipment placement and high door opening frequency. This paper presents an overview of various methods used for assessing the IAQ in hospital facilities, especially in an operating room, isolation room, anteroom, postoperative room, inpatient room and dentistry room. This review shows that both experimental and numerical methods demonstrated their advantages in the IAQ assessment. It was revealed that both airflow and particle tracking models could result in different particle dispersion predictions. The model selection should depend on the compatibility of the simulated result with the experimental measurement data. The primary and secondary forces affecting the characteristics of particle dispersion were also discussed in detail. The main contributing forces to the trajectory characteristics of a particle could be attributed to the gravitational force and drag force regardless of particle size. Meanwhile, the additional forces could be considered when there involves temperature gradient, intense light source, submicron particle, etc. The particle size concerned in a healthcare facility should be less than 20 µm as this particle size range showed a closer relationship with the virus load and a higher tendency to remain airborne. Also, further research opportunities that reflect a more realistic approach and improvement in the current assessment approach were proposed.

Influence of the Internal Structure Type of a Large-Area Lower Exhaust Workbench on Its Surface Air Distribution.

Local exhaust ventilation is an important method of contamination control, and the type of exhaust hood and the air distribution at the hood face have an important influence on the contamination control effect. When the hood face is large, it is difficult to create a uniform airflow distribution at the hood face, which if achieved, could improve the effect of contamination control. To that end, the large-area workbench used in the process of vaccine purification was taken as the research subject prototype for this study. According to the methods for generating a uniform airflow distribution at the hood face, the lower exhaust workbenches of four structures were established using CAD and simulated using Ansys Fluent. The best uniformity of workbench surface air distribution was with Structure-4, while the worst was with Structure-1. The workbench surface airflow distribution could not achieve uniformity when only an inclined bottom was used for the large-area lower exhaust workbench with one side outlet. The more internal slits there were, the greater the air distribution area and the more uniform the air distribution. The width of the area of workbench surface airflow distribution was determined by the width of the slits. The numerical simulation results were verified by experiments, which showed them to be credible.

An Air Velocity Monitor for Coal Mine Ventilation Based on Vortex-Induced Triboelectric Nanogenerator.

Air velocity of coal mine ventilation is an important consideration that may cause serious damage. This paper proposes a simple, low cost and effective air velocity monitor (AVM) for coal mine ventilation. The AVM uses the lock-in characteristic of vortex-induced vibration (VIV) to sense the air velocity. Amplitude of the VIV is converted into frequency signal of a vortex-induced triboelectric nanogenerator (VI-TENG) to improve the durability. Structure of the AVM are designed, and parameters of the AVM are optimized with experiments. For the upper and lower air velocity thresholds of 3.1 and 3.6 m/s, the optimized flexible beam length, slider weight, electrode space and electrode width are 42.5 mm, 0.4 g, 0.2 mm and 0.5 mm, respectively. Experiments also show that the output frequency of the VI-TENG could represent the amplitude of VIV well with the correlation coefficient of 0.93. Durability test demonstrates that the AVM generates stable output frequency in 120,000 cycles. A prototype and its controller are fabricated. Wind tunnel tests of this prototype show that it can give alarm when the gas velocity goes above the upper threshold or below the lower threshold. The proposed AVM could be a good solution for simple and effective coal mine ventilation alarm.

Rapid Robot-Aided On-site Testing of Fume Cupboards.

Although containment testing of fume cupboards (FC) according to the standards EN 14175-3 (2019) or ANSI/ASHRAE 110 (2016) is well established for type testing, its application is currently much less accepted and practised for evaluating containment on-site. Few of the several million FC in the market have been tested at installation and commissioning, and even less undergo verification of containment during their service life in the laboratories. Several reasons have led to this unsafe situation. To address this challenge, a new concept has been developed to allow for rapid on-site testing of FC to gain knowledge as to the functional efficiency as well as to safety aspects for the operator. The concept consists of a movable robot-aided test equipment that can be installed quickly to the FC in running labs. Multiple sensors detect the tracer gas isopropanol. Within a test run of only 10-min data is collected to quantify containment at the sash opening and to determine purge efficiency. The method reveals impact from interfering effects such as draughts, air distribution, and movements and from equipment installed, and is a tool for the optimization of operating conditions of a lab. This article presents an advanced alternative to the existing containment tests, particularly for on-site testing. The method assesses not only proper operation of the FC in its environment, but also the suitability of a FC for a given use under aspects of health and safety evaluation.

Effects of medical staff's turning movement on dispersion of airborne particles under large air supply diffuser during operative surgeries.

The present study examines the effect of medical staff's turning movements on particle concentration in the surgical zone and settlement on the patient under single large diffuser (SLD) ventilation. A computational domain representing the operating room (OR) was constructed using computer-aided design (CAD) software. The airflow and particle models were validated against the published data before conducting the case studies. The airflow in the OR was simulated using an RNG k-ε turbulence model, while the dispersion of the particles was simulated using a discrete phase model based on the Lagrangian approach. A user-defined function (UDF) code was written and compiled in the simulation software to describe the medical staff member's turning movements. In this study, three cases were examined: baseline, SLD 1, and SLD 2, with the air supply areas of 4.3 m2, 5.7 m2, and 15.9 m2, respectively. Results show that SLD ventilations in an OR can reduce the number of dispersed particles in the surgical zone. The particles that settled on the patient were reduced by 41% and 39% when using the SLD 1 and SLD 2 ventilations, respectively. The use of the larger air supply area of SLD 2 ventilation in the present study does not significantly reduce the particles that settle on a patient. Likewise, the use of SLD 2 ventilation may increase operating and maintenance costs.

Aerosol particle emission increases exponentially above moderate exercise intensity resulting in superemission during maximal exercise.

Many airborne pathogens such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are transmitted indoors via aerosol particles. During exercise, pulmonary ventilation can increase over 10-fold, and therefore, exercisers will exhale a greater volume of aerosol-containing air. However, we currently do not know how exercise affects the concentration of aerosol particles in exhaled air and the overall emission of aerosol particles. Consequently, we developed a method to measure in parallel the concentration of aerosol particles in expired air, pulmonary ventilation, and aerosol particle emission at rest and during a graded exercise test to exhaustion. We used this method to test eight women and eight men in a descriptive study. We found that the aerosol particle concentration in expired air increased significantly from 56 ± 53 particles/liter at rest to 633 ± 422 particles/liter at maximal intensity. Aerosol particle emission per subject increased significantly by a factor of 132 from 580 ± 489 particles/min at rest to a super emission of 76,200 ± 48,000 particles/min during maximal exercise. There were no sex differences in aerosol particle emission, but endurance-training subjects emitted significantly more aerosol particles during maximal exercise than untrained subjects. Overall, aerosol particle emission increased moderately up to an exercise intensity of ∼2 W/kg and exponentially thereafter. Together, these data might partly explain superspreader events especially during high-intensity group exercise indoors and suggest that strong infection prevention measures are needed especially during exercise at an intensity that exceeds ∼2 W/kg. Investigations of influencing factors like airway and whole-body hydration status during exercise on aerosol particle generation are needed.

Jet stream position explains regional anomalies in European beech forest productivity and tree growth.

The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.

Quantitative evaluation of chemical fume hoods performance by CO2 tracer gas.

BACKGROUND: Various chemical substances and carcinogens have been presented in medical sciences universities' educational and research laboratories. For this purpose a suitable ventilation system had to be implemented to ensure the correct operation of the hoods. OBJECTIVE: To evaluate the performance of laboratory chemical fume hoods of the University of Medical Sciences using a novel quantitative method. METHODS: In this study, 43 chemical fume hoods were investigated in the laboratories of the University of Medical Sciences. The technical specifications of the hoods and their compliance with the standard have been investigated. The hoods face velocity was measured using a thermal anemometer. Quantitative evaluation was performed using the new method of CO2 tracer gas and the results were analyzed using SPSS software version 19. FINDINGS: The hoods presented both favorable and unfavorable results in terms of technical specifications and location. The results showed 50.2% of the hoods have visible leakage. Hood face velocity was not suitable for any of the hoods in the case fully open.when half open only 16.3% of the hoods and in the case of 25% open face, 34.9% of the hoods had a good velocity. Most hoods have CO2 leakage even at small amounts. CONCLUSIONS: the unsuitable performance of the hoods is mainly due to the unsuitability of the fans, furthermore investigation and correction of technical problems are required. The new quantitative method is a suitable method for routine evaluating chemical fume hoods and can replace the SF6 gas tracer method.

Analysis of Infection Transmission Routes through Exhaled Breath and Cough Particle Dispersion in a General Hospital.

Identifying infection transmission routes in hospitals may prevent the spread of respiratory viruses and mass infections. Most previous related research focused on the air movement of passive tracers, which typically represent breathing. In this study, particle evaporation and dispersions with various particle sizes were applied to evaluate particle movement because of breathing and coughing using computational fluid dynamics (CFD) simulations. Pyeongtaek St. Mary Hospital, where a Middle East respiratory syndrome (MERS) index patient infected several patients on the same floor, was used for a case study. We compared the dispersion characteristics of various particle sizes and validated results by comparing infection rates in different ward. Results indicated that droplets spread across the corridor and dispersed to wards that were more than 17 m apart from the index patient by natural ventilation. Droplets from exhaled breath under steady-state simulation showed a wider range of dispersion than cough droplets under transient simulation, but cough droplet dispersion was more consistent with the actual infection rate in each ward. Cough droplets sized under 75 µm evaporated to 26% of the initial size and started to disperse into the corridor within one minute; in nine minutes, droplets dispersed throughout every ward. This study may increase awareness on the dispersion characteristics of infectious particles.

Changing Patterns of the Flow Ratio with the Distance of Exhaust and Supply Hood in a Parallel Square Push-Pull Ventilation.

The method of flow ratio k is often used for designing parallel push-pull ventilation. The k value is mostly selected empirically and is difficult to determine accurately, resulting in an imprecise design of the push-pull ventilation system. Therefore, parallel push-pull ventilation was taken as the research object in this paper. The push-pull ventilation studied consists of a square uniform supply hood and a square uniform exhaust hood, and the side length of pull hood and pull hood was same. A workbench was set between the push hood and pull hood, and the source of toluene pollutions was set in the center of the worktable surface. The optimal k values for different distances between push hood and pull hood were studied by numerical simulation using Ansys Fluent, which were obtained base on the distribution of wind speed and toluene concentration. The results showed that parallel push-pull ventilation is not suitable for applications when L/a ≥ 6. The changing patterns of k value with L/a is proposed in the range of 1.5 ≤ L/a ≤ 5 for the parallel square push-pull ventilation, which can be used to estimate k value relatively accurately under the condition that L/a is known, so as to guide the determination of the exhaust air volume of the parallel push-pull ventilation system.

Effects of location, classroom orientation, and air change rate on potential aerosol exposure: an experimental and computational study.

This study examined the dispersion of potentially infectious aerosols in classrooms by means of both a CO2 tracer gas, and multizone contaminant transport modeling. A total of 20 tests were conducted in three different university classrooms at multiple air change rates (4.4-9.7/h), each with two different room orientations: one with the tracer gas released from six student desks toward the air return, and one with the same tracer gas released away from it. Resulting tracer concentrations were measured by 19 different monitors arrayed throughout the room. Steady-state, mean tracer gas concentrations were calculated in six instructor zones (A-F) around the periphery of the room, with the results normalized by the concentration at the return, which was assumed to be representative of the well-mixed volume of the room. Across all classrooms, zones farthest from the return (C, D) had the lowest mean normalized concentrations (0.75), while those closest to the return (A, F) had the highest (0.95). This effect was consistent across room orientations (release both toward and away from the return), and air change rates. In addition, all zones around the periphery of the room had a significantly lower concentration than those adjacent to the sources. Increasing the ventilation rate reduced tracer gas concentrations significantly. Similar trends were observed via a novel approach to CONTAM modeling of the same rooms. These results indicate that informed selection of teaching location within the classroom could reduce instructor exposure.

Research on a push-pull industrial trough-side exhaust hood based on CFD simulation and experiment.

The traditional industrial trough-side exhaust hood requires large energy consumption for one-way airflow because the air inlet and outlet are on both sides of the industrial slot. In this research, based on the improvement of the traditional push-pull trough-side exhaust hood, a double-sided symmetrical push-pull industrial trough-side exhaust hood is researched. Simulation software ICEM and FLUENT were used to research the relationship between the distance of air inlet and outlet and the air volume ratio, and the relationship between the air volume ratio and mass fraction of pollutant gases, using carbon monoxide as the pollutant gas. The research found that when the pollutant mass fraction reaches the specified level, the air inlet and outlet distance is quadratically related to the air volume ratio. When the distance between the inlet and outlet is 0.12 m and the corresponding minimum flow ratio is 1.7, the interference of the suction air outlet pressure on the blowing air outlet jet reaches the minimum. By comparing the energy consumption with the traditional industrial trough-side exhaust hood, the energy saving rate is 75.8% with the same pollutant control effect. The double-sided symmetrical push-pull industrial trough-side exhaust hood reduce the cost of treating and discharging pollutants and provides a new idea for industrial pollutant treatment.

Design of an array of piezoresistive airflow sensors based on pressure loading mode for simultaneous detection of airflow velocity and direction.

As an irreplaceable element for obtaining airflow information in many engineering scenarios, airflow sensors have gained increasing attention across the fields of aerospace engineering, environmental engineering, sustainable energy exploitation, meteorology research, and so on. As one of the mainstream airflow sensing principles, piezoresistive airflow velocity sensors have experienced rapid growth over the years, while effective vector airflow sensors with the ability of detecting both airflow velocity and direction based on the piezoresistive principle are scarce. Here, on the basis of our developed piezoresistive airflow velocity sensors based on pressure loading mode, we design an array of these sensors and propose a corresponding explicit algorithm for simultaneous detection of airflow velocity and direction. This sensor array configuration enables an automatic recognition function of the quadrant of incoming airflow, which can significantly simplify the reverse calculation of airflow information compared with conventional vector airflow sensors. The experimental results demonstrate the decent performance of this sensor array for identifying both airflow velocity and direction. This study not only fills the gap between our developed airflow velocity sensor and the ability of detecting airflow direction but also presents a simple and universal array-based strategy for vector airflow sensing, which could be widely applied in airflow sensors based on other principles.